The invention relates to a protective hose, particularly a cable guiding hose, for a robot having at least partly externally positioned cables, particularly supply cables for robot tools.
In the case of multiaxial robots with several parts pivotable relative to one another, particularly robot arms, in the case of robot movements spacing changes with respect to the individual parts occur, which must more particularly be taken into account with at least partly externally positioned protective hoses for guiding supply cables for elements and in particular tools of the robot. They must on the one hand be in a position to absorb length changes and on the other in the case of robot movements must undergo minimum loading in order to ensure a high stability and prevent premature damage. In particular the protective hose end located in the vicinity of the robot hand generally pivotable about three axes, due to extreme movements and orientation changes of the robot hand or a tool fixed thereto, is subject to high loading by tensile, compressive and bending stresses.
In order to ensure the protective hose elasticity necessary for absorbing robot hand movements, it is known to guide the same in compensating loops along the robot hand or a robot arm articulated thereto. As these compensating loops must have a certain dimensional stability, the protective hose is made from a relatively hard and consequently brittle material, e.g. polyamide (e.g. PA12), where its wall thickness must not exceed a certain limit in order to ensure the flexibility particularly necessary in the vicinity of the tool. This frequently leads to fatigue failures of the protective hose at its hand-side end and resulting periods of disuse of the robot.
In the case of a robot with at least partly externally positioned cables, the problem of the invention is to ensure an improved cable guidance, which does not or only slightly impairs the robot mobility as a result of a high elasticity and which in particular has a long service life, so as to largely avoid the periods of disuse of the robot caused by protective hose failure.
In the case of a protective hose of the aforementioned type, this problem is solved according to the invention in that a flexible hose end piece terminally positionable on the protective hose and whose wall thickness at least zonally changes over its length, the said wall thickness having a minimum value in the central area.
As a result of the construction according to the invention, the flexible hose end piece as a result of its greater wall thickness at both ends can be easily coupled both to the protective hose and to the tool, whilst simultaneously ensuring the necessary high flexibility due to its smaller wall thickness in the central area, without its overall strength being impaired. The flexible hose end piece gives the protective hose a long service life, in that it absorbs the movements of the robot hand or the tool and due to the construction according to the invention itself has a long service life.
According to a preferred embodiment the wall thickness of the starting area of the hose end piece roughly corresponds to the wall thickness of the protective hose and the wall thickness of the hose end piece in the starting area thereof more particularly roughly corresponds to the wall thickness in its end area. This gives the two ends of the flexible hose end piece an increased stiffness more particularly corresponding roughly to the protective hose stiffness, so that it can be readily coupled both to the protective hose and e.g. to the robot tool.
In order to prevent a failure of the flexible hose end piece in the immediate vicinity of the terminal connection points, the wall thickness of the hose end piece preferably substantially continuously decreases from its starting area to its central area and increases substantially continuously from its central area to its end area. Alternatively the wall thickness of the hose end piece can also decrease stepwise from its starting area to its central area and increase stepwise from its central area to its end area and in this case the hose end piece e.g. can comprise joined together hose segments having different wall thicknesses.
The hose end piece appropriately has a ring or helically corrugated wall, which in per se known manner gives it an increased flexibility. The wall of the hose end piece can e.g. be corrugated in a substantially rectangular, sinusoidal or sawtooth-like manner.
With such a hose end piece construction preferably its wall thickness mainly changes in the substantially axially positioned wall sections, whereas in the substantially radially wall portions it remains substantially constant. It has surprisingly been found that such a zonally differing wall thickness of the hose end piece brings about elasticity characteristics roughly corresponding to the continuously varying wall thickness and in particular the hose end piece flexibility is not or is only slightly impaired. This makes it possible e.g. to bring about an easy manufacture of the inventive hose end piece by extrusion, because during such an extrusion the material excess produced in the vicinity of the ends of the hose end piece is mainly accumulated in the axial wall sections and leads there to a greater wall thickness, whereas the thickness of the radial wall sections remains essentially unchanged.
Advantageously the starting area of the hose piece can be terminally fixed to the protective hose by means of a wearing ring. It is advantageously fixable at the end remote from the protective hose to the robot or robot tool by means of a hose clip.
As a function of the robot dimensions, the hose end piece length preferably is between 50 and 1000 mm, particularly between 100 and 500 mm.
Whilst the protective hose can be made from conventional hard, brittle and consequently relatively dimensionally stable material, the flexible hose end piece is preferably made from a softer, wear-resistant material, so that it is mainly the hose end piece which absorbs the robot movements.
The invention also relates to a hose end piece for a protective hose of the aforementioned type and to a robot with at least partly externally positioned cables, which is equipped with a protective hose having such a hose end piece.